Method for improving the surface of thermoset coatings

ABSTRACT

Method for improving the leveling properties of thermosetting coating powders which comprises including in the powder composition solid, finely divided glyceryl tris(12hydroxystearate).

United States Patent 1191 Blackley et al.

Minn.

[22] Filed: Feb. 2, 1973 [21] Appl. No.: 329,219

[52] US. Cl. 260/31.6 [51] Int. Cl C08g 51/36 [58] Field of Search260/316, 79.5 NV, 80.81

[56] 3 References Cited UNITED STATES PATENTS 2,396,997 3/l946 Fryling260/795 NV June 28, 1974 8/1965 Smith etal 106/316 6/1970 Fellers etall 1. 260/808] Primary ExaminerLewis T. Jacobs Assistant ExaminerE.Suzanne Parr Attorney, Agent, or Firm-Alexander, Sell, Steldt &DeLal-lunt ABSTRACT Method for improving the leveling properties ofthermosetting coating powders which comprises including in the powdercomposition solid, finely divided glyc eryl tris( 12-hydroxystearate).

16 Claims, N0 Drawings SUMMARY OF THE INVENTION This invention relatesto a method for improving the leveling properties of thermosettingcoating powders which comprises including in the powder compositionsolid, finely divided glyceryl tris(12-hydroxystearate).

BACKGROUND OF THE INVENTION The powder coating technique in generalinvolves application of a finely divided organic powder to an articleand the subsequent conversion of the powder through application of heatto an adherent continuous coating. It is particularly well suited tomodern assembly line operation, especially when protective and/ordecorative coatings are to be applied to metal articles. The organicpowder is applied to the article by one of the known methods, such asthe fluidized bed and electrostatic spray methods, and then heated tocause it to fuse and flow into a continuous coating on-the article beingcoated and to subsequently become thermoset. The thermoset coatingsresulting from these powders are tough, solvent resistant and weatherresistant. Unless pigments, dyes or other such materials are added, theyare clear and highly glossy.

Thermosetting powder coatings have certain recognized advantages, bothin the coating process and in the properties of the final coating. Thus,no solvent or primer is needed, single coat coverage is possible andthere is no sagging of the film. Also, there is often an improvedhardness-flexibility relationship and the films have more universalchemical and solvent resistance.

Among the classes of thermosetting coating powders are those based onepoxy, polyester and acrylic systems. These may be combined and/ormodified, e.g., epoxy-acrylic and polyester-acrylic systems can be used.They can also be modified with other crosslinking components such asunsaturates and aminoplasts. More extensive information relative to thethermosetting powder coating field is provided in the review entitledThermosetting Polyester and Acrylic Powder Coatings," D. D. Taft, R.Hong and W. J. McKillip, publication number FC 72-942 of the Society ofManufacturing Engineers, 20501 Ford Road, Dearborn, Mich., 48128.

One economically important difficulty with powder coated surfaces is anaesthetic one, i.e., their characteristic orange peel appearance. Thisis caused by their characteristic surface configuration which gives anappearance similar to that of the peeling of an orange. Agents whichhave been used in the past to reduce the orange peel have had theadditional effect of increasing the blocking of the powder (i.e., thetendency of the particles to agglomerate, resulting in failure of thepowder to flow freely and thereby make coating difficult or impossible).Thus, attempts to alleviate one serious problem in powder coatings hasbrought on another problem which has been perhaps, more serious.

THE PRESENT INVENTION It is an object of the present invention toprovide a method for improving the leveling properties of thermosettingcoating powders without at the same time bringing about substantialblocking which comprises 2 including in the powder composition glyceryltris(12- hydroxystearate).

It is a further object of the invention to provide thermosettablecoating powder compositions containing an epoxy, acrylic and/orpolyester prepolymer system and glyceryl tris( 12-hydroxystearate). I

In accordance with the present invention there is provided a method forimproving the leveling properties of thermosetting epoxy, acrylic andpolyester coating powders which comprises including in the powdercomposition from one to ten parts by weight of glyceryltris(12-hydroxystearate), based on 100 parts of the prepolymer portionof the composition. Glyceryl tris(12-hydroxystearate) is a hydrogenatedcastor oil having an hydroxyl equivalent weight of about 185. It is awax with a melting point of from about 84 to 87 C. and an iodine valueof 3-6 and is available from the Baker Castor Oil Company of Bayonne,New Jersey under the trade designation Castorwax." Preferably thecoating powders are of the acrylic type.

The basic epoxy acrylic and polyester polymer systems include mixturesthereof (e.g., epoxy-acrylics and polyester acrylics) as well as totalsystems of each type. Furthermore, they can be modified with othercrosslinking components such as unsaturates and aminoplasts. All ofthese are included in the general terms epoxy, acrylic and polyesterpolymer systems as used herein.

A particularly preferred method of the invention can be expressed asfollows:

A method for improving the leveling properties of a thermosettingcoating powder containing 1. 100 parts of a solid, low molecular weight,substantially linear, storable epoxy-functional acrylic terpolymer of5-20 parts glycidyl methacrylate units,

5-35parts of lower alkylacrylate units in which the alkyl group containsfrom two to four carbon atoms, 50-70 parts of methyl methacrylate units,and 05-10 parts of chain terminating groups selected from O B Rodentsuid11 5%;

wherein R is an alkyl group containing not more than 20 carbon atoms,said terpolymer having a. a glass transition temperature of from 20 toC., b. a Durrans melting point of from 90 to 170 C.,

c. a melt index of from 1 to 30, at a temperature of 152 C., with apiston loading of 1,200 grams and an extrusion orifice of 0.0465 inches,and

d. an epoxy equivalent weight of 700-3,000

2. 0-20 parts of a crosslinking agent selected from saturated aliphaticdicarboxylic acids having from five to 20 carbon atoms which isessentially unreactive at room temperature but which reacts rapidly 1above 150 C.

3. 0-40 parts of an acid-terminated linear polyesterplasticizer-curvature having an equivalent weight per carboxyl group offrom to 1,500 and 4. 0.1 to 5 parts of a non-ionic aliphatic polyacrylate surface active agent,

provided that the ratio of total carboxyl equivalence of (2) plus (3) is05-15:] of the epoxy equivalence of (1),

said method comprising including in the said powder, as an additionalconstituent thereof 5. ll parts of glyceryl tris( l2-hydroxy-stearate).

Preferably the terpolymers contain from to parts of glycidylmethacrylate, to parts of the lower alkyl acrylate and 60 to 65 parts ofmethyl methacrylate. The lower alkyl acrylate is ordinarily ethylacrylate.

The glass transition temperature is that temperature range at which anamorphous polymer changes from a brittle glassy state to a flexiblerubbery state. This has been characterized in the terpolymers herein bythe temperatures at which the material exhibits a discontinuous changein heat capacity as measured by differential thermal analysis. Themelting point measurements herein were made by the Durrans mercurymethod and the melt index measurements were made according to ASTM-Dl238at a temperature of 152C., a piston loading of 1,200 grams and anextrusion orifice of 0.0465 inches.

The terpolymers are prepared by agitating in an inert atmosphere 1. anaqueous medium containing a suspending aid,

2. a monomer charge of 5-20 parts of glycidyl methacrylate, 5-35 partsof a lower alkyl acrylate in which the alkyl group contains from two tofour carbon atoms and 50-70 parts of methyl methacrylate,

3. 0.5-10 parts of a chain transfer agent of the formula RoboHisH or(It-OH! s wherein each R is an alkyl group containing not more than 20carbon atoms, and

4. 005-5 parts of a free radical initiator, at from 60 to 90 C. for notless than 2 hours.

Thus, the preparation of the polymers is carried out in the absence of asolvent for the polymer by a suspension polymerization technique.Preferably, a mixture of the monomers, the chain transfer agent and theinitiator is added to a heated, stirred, aqueous solution of thesuspending agent under an inert (e.g., nitrogen) atmosphere. After theaddition is complete, the agitation and heating are maintained for notless than 2 hours and ordinarily for not more than 10 hours. The polymeris recovered by cooling the mixture, filtering, washing and drying. Theresulting product is free-flowing polymer beads, suitable for subsequentprocessing. Alternatively, the initiator may be suspended in the aqueousphase and the monomer mixture added in small increments. This processresults in the preparation of a relatively low molecular weightterpolymer with substantially complete conversion of the monomerscharged to polymer. The suspension polymerization technique of thisprocess avoids the substantial loss of low molecular weight componentsof polymer (often characteristic of the isolation step in solutionpolymerizations which involve the precipitation of the polymer fromsolution by means of a non-solvent). The retention in the product of thelow molecular weight components, furthermore, is advantageous in that itaids in the thermal flow of the polymer in the fusion step of the powdercoating operation.

As noted previously, the terpolymers have a melt index within aparticular range. In order to control this, and the molecular weight ofthe polymer, particular chain transfer agents are used, i.e., compoundsof the formulae ROi'JCHiSH and (R-OST wherein each R is an alkyl groupcontaining not more than 20 carbon atoms. These particular classes ofchain transfer agents have been found to be particularly useful sincethey not only control the molecular weight (and hence the melt index) ofthe resulting polymer to the desired degree but also they do not inhibitthe complete conversion of monomers to polymer. When commonly used chaintransfer agents, such as lauryl or dodecyl mercaptan, are used atsufficient levels to produce a polymer having the desired melt index, aproduct with an unacceptable amount of residual monomer is produced. Toreduce the amount of monomer in the product to an acceptable level, upto 10 percent by weight of initiator may be required. In the practice ofthe present process, however, using the preferred chain transfer agent,relatively low levels of initiator are sufficient for substantiallypercent conversion of monomers to polymer.

Preferably in the chain transfer agents of the type 0 ROiCHaSH,

R is isooctyl. Such compounds in which R contains fewer than five carbonatoms are less effective and those in which R contains more than '1 1carbon atoms appear to be deleterious of suspension stability. In thechain transfer agents of the type R is preferably RCH wherein R ishydrogen or an alkyl group bonded to the Ch through a tertiary carbonatom (e.g., R is tert-butyl). The reason for this is that polymers madeusing chain transfer agents of the second type,

in which R is a group bearing hydrogen on the B carbon atom arethermally unstable.

Suitable free radical initiators for use in the process of the inventionare, for example, peresters, acyl peroxides, andazo compounds.Specifically these include benzoyl peroxide, lauroyl peroxide, t-butylperbenzoate, t-butyl peroxypivalate, dibenzyl peroxydicarbonate,diisopropyl peroxydicarbonate and azobis isobutyronitrile, ultravioletlight or ionizing radiation.

Either ionic suspending aids, such as poly(sodium acrylate) orpoly(ammonium acrylate) or non-ionic aids such as poly(vinyl alcohols)are suitable.

The crosslinking agents and plasticizer-curatives (i.e.,plasticizer-crosslinking agents) used in the thermosetting coatingpowders are polycarboxylic (preferably dicarboxylic) or anhydride(preferably monoanhydride) type materials, ordinarily selected from thepolycarboxylic acids and anhydrides themselves and acidterminatedpolyesters thereof. The ratio of the total carboxyl equivalency of thesematerials (constituents (2) and (3) of the coating powders) to the epoxyequivalence the terpolymer is 0.5-1.5:1.

Each anhydride group is considered to be equivalent to two carboxylgroups with respect to this ratio. The polycarboxylic acids andanhydrides can be aliphatic (e.g., alkanoic) or aromatic in nature andordinarily contain from five to 20 carbon atoms.

The acid-terminated polyesters are useful for introducing flexibilityinto the cured coatings (plasticizing them) and for preventing chippingand flaking of the coatings, due to their longer chains. It isfrequently preferred to utilize a mixture of crosslinking agents andplasticizer-curatives, ordinarily one of each. A particularly preferredcrosslinking-plasticizing system is -20 parts of an acid terminatedbutanediol adipate having an acid equivalent weight of 500-l,000combined with an alkanoic dicarboxylic acid containing from five to 20carbon atoms, so that the ratio of the total carboxylic acid equivalenceis 0.9-1.1:1 of the epoxy equivalence of the terpolymer.

The surface active agents provide good substrate wetting. When nosurface active agent is present, the molten coating often does not wetthe substrate surface sufficiently to give an optimum uniform coatingand small imperfections (pocks) form in which the coating is very thin.These pocks are effectively eliminated by adding 0.1-5 parts, preferably0.2-1.5 parts, based on 100 parts of terpolymer, of a non-ionicaliphatic polyacrylate surface active agent. This can be an aliphaticpolyacrylate, such as poly(2-ethylhexylacrylate).

Although the powder coating compositions can be used without catalysts,it is preferred that a catalyst be included to facilitate thecrosslinking reaction and thus enhance the solvent resistance andabrasion of the resulting coating. The higher rate of reaction broughtabout by the catalyst is also an advantage. The catalysts areadvantageously used in amounts varying from about 0.05-2 parts (based on100 parts of terpolymer). They are of the types which promote theacid-epoxy crosslinking reaction and/0r promote the epoxy-epoxypolyetherification cross-linking reaction. The amount of catalyst usedwill vary with the specific crosslinking agent and its concentration aswell as the specific time and temperatures used in thesintering-thermosetting coating process. The catalysts which are used donot significantly enhance the rate of reaction at room temperature (thatis to say they are latent at that temperature) but become active atparticular selected higher temperatures. The catalysts that are latentup to at least 50 C. are preferred. Catalysts for the epoxy-carboxylicreaction are useful in sthe coating powders of the invention provided,most preferably, that they can be incorporated into the powder withoutcausing blocking over a period of 6 months at 50C., and provided furtherthat they do not cause foaming during the curing cycle.

Useful catalysts include heavy metal salts of organic acids (ordinarilythose containing from two to 22 carbon atoms) such as stannouscarboxylic acid salts including stannous octoate and stannous stearate,tertiary or quaternary amines and their halides, such astrimethylbenzylammonium chloride and 2- methylimidazole. A preferredcatalyst for a dicarboxylic acid cross-linked system is 0.08-0.5 partsof stan nous stearate per parts of terpolymer. This small amount ofcatalyst improves the flexibility, impact resistance and solventresistance.

Additionally, up'to about 60 percent by weight of the coating powder ofone or more additives such as pigment's, dyes, fillers (inorganic ororganic), metallic flakes, ultraviolet absorbers, etc., can be added tothe powders. Thus, fillers or extenders such as mica, silica, calciumcarbonate, barytes, etc., can be used to increase the hardness and/orreduce the costs of the finished products. Pigments or dyes, such asphthalocyanine blue, titanium dioxide, chromium oxide, carbon black, andthe acrylamide yellows or oranges. etc., may be incorporated into thecoating powders for the purpose of coloring or opacifying the resultingcoatings. Metallic flakes such as aluminum may be incorporated into thecoating powders to lend decorative effects to the resultant coatings.

The thermosettable coating powders are prepared by dissolving orthoroughly dispersing all of the constituents in a suitable solvent.These include ketones, esters, aromatic hydrocarbons, chlorinatedhydrocarbons and ethers, which are readily removed by distillation.Amont the preferred solvents are acetone, ethyl acetate, benzene,tetrahydrofuran and methylene chloride. Once the constituents arethoroughly mixed, the solvent is evaporated under vacuum, leaving asolid cake which is crushed into a fine powder. Alternatively, thecoating powder can be prepared by mixing the powdered constituentstogether and homogenizing the mixture by processing it through a mixingextruder or on a two roll mill and grinding to less than micron particlesize powder.

The following examples are given for the purpose of further illustratingthe present invention, but are not intended, in any way, to be limitingon the scope thereof. All temperatures herein are given in degreesCentigrade and the parts are expressed by weight.

TERPOLYMER PREPARATION EXAMPLE 1 A mixture of 62.4 parts (423 grams) ofmethyl methacrylate, 24.0 parts (163 grams) of ethyl acrylate, 13.6parts (92 grams) of glycidyl methacrylate, 3.9 parts (26.5 grams) ofisooctyl mercaptoacetate wherein R is isooctyl) and 3.5 parts (23.6grams) of benzoyl peroxide was added with stirring to 250 parts (1700grams) of 0.] percent aqueous poly(sodium acrylate) at 60 under anitrogen atmosphere. The mixture was stirred for 5 hours at 60 thencooled, filtered, washed and dried.

The resulting polymer had a melt index of 5.3, a melting point of 134and a glass transition temperature, T,,, of 28. The epoxy equivalentweight was found to be 1,199 as compared to a calculated value of 1,127.

EXAMPLE 2 To 225 parts of a stirred 0.l percent aqueous solution ofpoly(sodium acrylate) at a temperature of 68 was added a mixturecomposed of 62 parts of methyl methacrylate, 24 parts of ethyl acrylate,14 parts of glycidyl methacrylate, 3.9 parts of isooctyl mercaptoacetateand 3.5 parts of benzoyl peroxide. The reaction temperature dropped to60 and was held there, with stirring for hours. The mixture was cooledand filtered, the solids washed with water and dried to give 93 percentof the theoretical amount of polymer beads with a melt index of 2.2, amelting point of 154 an epoxy eauivalent weight of 1,262 and a glasstransition temperature of 41.

EXAMPLE 3 The polymerization was carried out as in Example 2 except thatthe benzoyl peroxide was suspended in the aqueous phase at 60, themixture of monomers and isooctyl mercaptoacetate added, and thepolymerization carried out at 77. The product had a melt index of 3.8, amelting point of 142 C., an epoxy equivalent weight of 1,240 and a glasstransition temperature of 46.

Chain Transfer Agents IOM isooctyl mercaptoacetate (H 11 s h dimethyldixanthogen dineopentyl dixanthogen nBuM n-butyl mercaptoacetate Dodec Mdodecyl mercaptoacetate Free Radical lnitiators BPO benzoyl peroxideAIBN azobisisobutyronitrile Aqueous phase Free radical Monomers, partsChain transfer agent initiator Example Susp. agent and number MMA EA GMAeoncn. Parts Agent Parts Initiator Parts 67 19 14 0.2% PVA 250 IOM 4.9AIBN 0.16 59 34 7 0.1% P(NaA) 350 IOM 3.0 BPO 1.4 52 28 0.1% P(NaA) 3302.4 BPO 1. 1 62 24 14 0.1% P(NaA) 250 3.9 BPO 3.5 62 24 14 0.2% PVA 2403. 9 AIBN 0.16 62 24 14 0.2% PVA 310 2. 9 .AIBN 0.4

62 24 14 0.2% PVA 310 3. 1 BPO 1. 2

15 62 24 14 0.2% PVA 310 IS 4. 7 BPO 1. 2

O( J S 16 62 24 14 0.1% PVA 310 nBuM 2.8 BPO 2.3 17 v 62 24 14 0.1%I(NaA) 310 Dodcc M 3.7 BPO 1. 2

h 1 Aqueous phase described in terms 01 the concentration 01 theparticular suspending agent in the aqueous p ase.

EXAMPLES 4-7 Four additional polymer lots according to the inventionwere prepared using the procedure of Example 1. The first three(Examples 4-6) were run in 300 gallon kettles, utilizing 700 poundmonomer charges and the fourth (Example 7) was run in a gallon kettleutilizing a 115 pound monomer charge. The physical properties of theresulting polymers were as follows:

Example Melting Melt Epoxy Eq. No. Point C Index Tg C Weight 4 I39 1.542 1197 5 124 10.1 37 I188 6 132 6.5 36 I 190 7 107 23.3 34 l 165EXAMPLES 8-17 Time & Example Durrans Melt Epoxy Temp.

No. m.p., Index Tg.C Equivalent of C Weight Polymn.

8 130 5.2 49 1105 4 hrs 9 123 10.2 33 2205 2 hrs 80 and 2 hrs 10 135 1.442 805 3 hrs 80 11 134 5.3 28 1199 5 hrs 60 12 117 14.1 29 1205 4 hrs 8013 126 5.4 50 1265 5 hrs 80 14 130 11.6 1362 2 hrs 80 and 3 hrs 90 15134" 4.6 1250 2 hrs I10" and I6 143' 2.6 1315 2 hrs 80" and 3 hrs 90 17134 6.0 I232 2 hrs 80 and 3 hrs 90 EXAMPLE 18 A mixture of 62 parts ofmethyl methacrylate, 24 parts of ethyl acrylate, 14 parts of glycidylmethacrylate, 1.9 parts of dodecyl mercaptan and 1.6 parts of benzoylperoxide was added with stirring to 340 parts of 0.1 percent aqueouspoly(sodium acrylate) at 60 under a nitrogen atmosphere. The mixture wasstirred for 3 hours at 80 then cooled, filtered, washed, and dried.

THE THERMOSETTING COATING POWDER FORMULATIONS EXAMPLE 19 The followingwere blended on a 6 inch two roll rubber mill:

Terpolymer of Example 3 100 Poly 2-ethyl hexyl acrylate (Modaflow,

available from Monsanto) l. Butanediol adipate (l) 10. Glyceryl tris(l2-hydroxy stearate) (2) 3. Titanium dioxide pigment 48. Black pigment0. Stannous stearate 0. Sebacic acid 7.

1) Acid terminated butanediol adipate with an acid equivalent weight of815.

(2) Available from The Baker Castor Oil Co., Bayonne, NJ. under thetrade designation Castorwax."

The terpolymer and the surface active agent were banded on the rolls ofthe mill with one roll heated at l35C. and the other roll cooled withcold water. The heat was then reduced to 38C. and the remainingcomponents added in approximately the order listed. Once intimatelyblended (after minutes), the material was removed from the mill as asheet, cooled and ground in a micropulverizer grinder containing anumber screen and the resulting powder was screened with a US. StandardNo. 230 screen. The portion which passed through the 230 mesh screen wasthen electrostatically sprayed at room temperature onto a metal testpanel (surface treated cold rolled 20 gauge steel panel with a zincphosphate surface treatment designated Bonderite 40 and available fromthe Parker Co. Detroit, Mich.) and the coated panel was cured 20 minutesat 177C. in a forced air oven.

The resulting gray colored coating was superior to known acrylic powdercoatings in gloss, lack of orange peel, flexibility and weathering. Italso passed an MEK rub test, resisted exposure to a 10 day salt spraytest and passed a 180 bend test without cracking. Other colors werereadily prepared by replacing the black and white pigments with pigmentsof other colors.

The MEK rub test consists of 30 circular wipes at light hand pressurewith a pad of 50 grade cheese cloth saturated with methyl ethyl ketone.In order to pass this test the coating must not be scratched or removed,either by disappearance of thefilm from the steel panel or by colortransfer to the pad. The salt spray test is designated ASTM 8117. In the180 bend test, a Q panel (a standard test panel approximately 4 by 8inches of untreated 20 gauge cold rolled steel conforming to ASTMspecification A 109) was coated to a thickness of approximately 2 milsand a corner was slowly bent l80. The bend was inspected for cracking,

chipping or flaking.

EXAMPLE 20 The following systems were prepared, coated and cured as inExample'l9 then evaluated to demonstrate the beneficial effectof theacid terminated butanediol adipate.

Terpolymer of Example 3 Poly 2-ethyl hexyl acrylate Glyceryl tris (l2-hydroxy stearate) 5 Sebacic acid 8.

Bulanediol adipate (as in Example 19) Black pigment Stannous stearateThe incorporation of the butanediol adipate made the coating moreflexible and impact resistent. Thus, the coated panels were subjected toa 50 pound impact test (ASTM 2794-69) and assigned ratings on thefollowing basis Rating 1. No cracking 2. Slight cracking 3. Considerablecracking 4. Extensive cracking withflaking The panels were rated asfollows:

Formulation No. Rating A 3 B 34 C 23 D 2 EXAMPLE 21 The systems of thisexample were prepared, coated and cured as in Example 19 then evaluatedto demonstrate the effect of the melt index of the terpolymer on 0 theresulting coatings.

Molt lndcx The coating of Lot B exhibited the least orange peel, Lot Cwas intermediate and Lot A the most orange peel.

EXAMPLE 22 The following samples were made and evaluated in the mannerdescribed in Example 19 to demonstrate the use of diacids ascrosslinking agents.

Components A B C D Terpolymer of Example 3 100 100 100 100 Poly 2-ethylhexyl acrylate 2.0 2.0 2.0 2.0 Glyceryl tris (12- hydroxy stearate) 5.05.0 5.0 5.0 Dodecanedioic acid 7.5 Adipic acid 5.17 Azelaic acid 6.67Sebacic acid 7.17 Butanediol adipate (as in Example 19) 10.0 10.0 10.010.0 Black pigment 2.5 2.5 2.5 2.5 Stannous stearate .084 .084 .084 .084

Tests 180" Bend pass pass pass pass Gel time of powder (sec) 35 35 35 37Solvent Rub (MEK) pass pass pass pass The rate and degree of cure couldbe controlled by the addition of catalysts such as, stannous stearate,stannous octoate and methyl imidazoles.

The bend and solvent rubtests are described hereinabove. The gel timetest is run as follows: A sample of powder is placed on a surface heatedto 204C. and the time required to reach a rubbery state is determined bystirring the molten resin and determining the point at which it becomesviscous and stringy. This time is recorded as the gel time.

EXAMPLE 23 A thermosetting coating powder containing only terpolymer,cross linking agent and surface active agent was prepared by dissolving100 parts of the terpolymer of Example 2, 0.49 parts of poly 2-ethylhexyl acrylate and 6.67 parts of adipic acid in 140 parts oftetrahydrofuran at room temperature. The tetrahydrofuran was removedusing a rotary evaporator and the remaining resinous composition waspulverized and dried overnight in a vacuum at room temperature. Thedried mixture was then micropulverized and screened to collect thematerial less than 53 mu in size.

The powdered composition obtained was electrostatically coated ontosteel panels and cured at 177C. for 20 minutes. The resulting finish wasa clear, glossy and transparent coating which was much more resistant tobreaking on bend, than a similar panel cured at 177C. for 3 minutes.This indicates the thermosetting nature of such compositions.

EXAMPLE 24 Th following lot demonstrates the use of a high catalystlevel.

Terpolymer of Example 2 100 Poly 2-ethyl hexyl acrylate 1.0 Adipic acid4.3 Butanediol adipate (as in Example 19) 20 Titanium dioxide pigment 31DOBP 2.0 Stannous stearate 1.0

The above powdered coating system had a gel time of 26 seconds and gavea 60 gloss reading of 84 when sprayed onto a test panel and cured. The60 gloss test conforms to ASTM D-1471-57T.

EXAMPLE 25 The following lots of thermosetting coating powdersdemonstrate the effects of glyceryl tris l2- hydroxystearate) in thecoating powders.

Lot A Lot B Terpolymer of Example 3 100 Poly 2-ethyl hexyl acrylate 1.51.5 Butanediol adipate as in Example 19 10.0 10.0 Glyceryl tris(12-hydroxy stearate) 0 3.3 Sebacic acid 7.0 7.0 Stannous stearate 0.080.08 Black pigment 0.67 0.67 Titanium dioxide pigment 47.8 47.8

These systems were prepared, coated and cured as in Example 19. Therewas no blocking of the powder in either lot. The final coating of Lot Bwas much better than the comparable coating (of equal thickness) of LotA with respect to orange peel, i.e. the coating of Lot B had much lessorange peel than that of Lot A.

More preferably in the preferred methods and compositions of theinvention, there are included 5-20 parts of component (2) and 5-40 partsof component (3), based on 100 parts of component (1), the terpolymer.

Particularly preferred is the method of the invention for improving theleveling properties of a thermosetting coating powder compositioncontaining 1. a solid, low molecular weight, substantially linear,

storable epoxy-functional acrylic terpolymer of 13-14 parts glycidylmethacrylate units, 23-24 parts of ethyl acrylate units,,59-60 parts ofmethyl methacrylate units and 3-4 parts of chain terminating groups ofthe formula wherein R is an isooctyl group, said terpolymer hav ing a. aglass transition temperature of from 30 to 60 b. a Durrans melting pointof from 1 10 to C.,

4. 12 parts of poly 2-ethyl hexyl acrylate said method comprisingincluding in the said powder. as an additional constituent thereof 5.3-4 parts of glyceryl tris(12-hydroxy-stearate).

Similarly preferred are the resulting compositions.

What is claimed is:

1. A method for improving the leveling properties of thermosettingepoxy, acrylic and polyester coating powders which comprises includingin the powder composition from one to ten parts by weight of glyceryltris(l2-hydroxystearate), based on 100 parts of the prepolymer portionof the composition.

2. A method according to claim 1 wherein the coating powder is anacrylic coating powder.

3. A method for improving the leveling properties of a thermosettingcoating powder containing l. 100 parts ofa solid, low molecular weight,substantially linear, storable epoxy-functional acrylic terpolymer of5-20 parts glycidyl methacrylate units, 5-35 parts of lower alkylacrylate units in which the alkyl group contains from two to four carbonatoms, 50-70 parts of methyl methacrylate units, and 0.5-10 parts ofchain terminating groups selected from ROl' JCH:S-aud 1106-8- wherein Ris an alkyl group containing not more than 20 carbon atoms,saidterpolymer having a. a glass transition temperature of from 20 to 70c., b. a Durrans melting point of from 90 to 170 C.,

c. a melt index of from 1 to 30, at a temperature of 152 C., with apiston loading of 1,200 grams and an extrusion orifice of 0.0465 inches,and

d. an epoxy equivalent weight'of 700-3000 2. 0-20 parts of acrosslinking agent selected from saturated aliphatic dicarboxylic acidshaving from five to 20 carbon atoms which is essentially unreactive atroom temperature but which reacts rapidly above 150 C. v

3. 0-40 parts of an acid-terminated linear polyesterplasticizer-curative having an equivalent weight per carboxyl group offrom 100 to 1,500 and 4. 0.1 to parts ofa non-ionic aliphatic polyacrylate surface active agent,

provided that the ratio of total carboxyl equivalence of (2) plus (3) is05-15:] of the epoxy equivalence of l said method comprising includingin the said powder, as an additional constituent thereof 5. 1-10 partsof glyceryl tris( l2-hydroxystearate).

4. A method according to claim 3 wherein the terpolymer contains -15parts of glycidyl methacrylate, 20-25 parts of lower alkyl acrylateunits and 60-65 parts of methyl methacrylate units.

5. A method according to claim 3 in which the lower alkyl acrylate isethyl acrylate.

6. A method for improving the leveling properties of a thermosettingcoating powder containing 1. a solid, low molecular weight,substantially linear, storable epoxy-functional acrylic terpolymer of13-14 parts glycidyl methacrylate units, 23-24 parts of ethyl acrylateunits, 59-60 parts of methyl methacrylate units and 3-4 parts of chainterminating groups of the formula wherein R is an isooctyl group, saidterpolymer having a. a glass transition temperature of from 30 to 60 C.,b. a Durrans melting point of from 1 10 to 150 C.,

c. a melt index of from 5 to 20. at a temperature of 152 C., with apiston loading of 1,200 grams and an extrusion orifice of 0.0465 inches,and

d. an epoxy equivalent weight of 1,100-1,300,

2. 7-8 parts of an aliphatic dicarboxylic acid containing nine to 10carbon atoms,

3. 8-12 parts of butanediol adipate having an equivalent weight percarboxyl group of 500-1000, and

4. l-2 parts of poly 2-ethyl hexyl acrylate, said method comprisingincluding in the said powder, as an additional constituent thereof 5.3-4 parts of glyceryl tris( l2-hydroxy-stearate).

7. A method according to claim 3 wherein the thermosetting coatingpowder contains 5-20 parts of (2) and 5-40 parts of (3).

8. A thermosetting coating powder composition of which the prepolymerportion is selected from epoxy, acrylic and polyester prepolymers, saidcomposition including from one to 10 parts by weight of glyceryltris(12-hydroxystearate), based on 100 parts of the prepolymer portionof the composition.

9. A thermosetting coating powder composition containing 0 S RO CH1S andRo -S- wherein R is an alkyl group containing not more than 20 carbonatoms, said terpolymer having a. a glass transition temperature of from20 to b. a Durrans melting point of from to 170 C., c. a melt index offrom 1 to 30, at a temperature of 152 C., with a piston loading of 1,200grams and an extrusion orifice of 0.0465 inches, and

d. an epoxy equivalent weight of 7003,000

2. 0-20 parts of a crosslinking agent selected from saturated aliphaticdicarboxylic acids having from five to 20 carbon atoms which isessentially unreactive at room temperature but which reacts rapidlyabove 150 C.

3. 0-40 parts of an acid-terminated linear polyesterplasticizer-curative having an equivalent weight per carboxyl group offrom to 1,500,

4. 0.1 to 5 parts of a non-ionic aliphatic poly acrylate surface activeagent and 5. 1-10 parts of glyceryl tris(12-hydroxy-stearate).

provided that the ratio of total carboxyl equivalence of (2) plus (3) is0.5-1.5:1 of the epoxy equivalence of l 10. A thermosetting coatingpowder composition containing 1. a solid, low molecular weight,substantially linear,

ll aocomswherein R is an isooctyl group, said terpolymer having a. aglass transition temperature of from 30 to 60 C b. a Durrans meltingpoint of from 1 10 to 150 C.,

c. a melt index of from 5 to 20, at a temperature of 152 C with a pistonloading of 1,200 grams and an extrusion orifice of 0.0465 inches, and

d. an epoxy equivalent weight of 1,1001,300,

2. 7-8 parts of an aliphatic dicarboxylic acid containing 9-10 carbonatoms, 3. 8-12 parts of butanediol adipate having an equivalent weightper carboxyl group of 500-1,000,

4. 1-2 parts of poly 2-ethy1 hexyl acrylate and 5. 3-4 parts of glyceryltris( l2-hydroxy-stearate). 11. A composition according to claim 10which contains 5-20 parts of (2) and 5-40 parts of (3).

12. A method for improving the leveling properties of a thermosettingcoating powder containing 1. 100 parts of a solid, low molecular weight,substantially linear, storable epoxy-functional acrylic terpolymer of5-20 parts glycidyl methacrylate units,

5-35 parts of lower alkyl acrylate units in which the alkyl groupcontains from two to four carbon atoms, 50-70 parts of methylmethacrylate units, and 0.5-10 parts of chain terminating groupsselected from O ROiiCHiS- wherein R is an isooctyl group, saidterpolymer having a. a glass transition temperature of from 20 to 70 C.,b. a Durrans melting point of from 90 to 170 C.,

3. 0-40 parts of a butanediol adipate having an equivalent weight percarboxyl group of from 100 to 1,500 and 4. 0.1 to 5 parts of polyZ-ethyl hexyl acrylate. provided that the ratio of total carboxylequivalence of (2) plus (3) is 05-15:] of the epoxy equivalence of lsaid method comprising including in the said powder, as an additionalconstituent thereof 5 1-10 parts of glyceryl tris( l2-hydroxy-stearate).

13. A method according to claim 12 wherein the terpolymer contains 10-15parts of glycidyl methacrylate, 20-25 parts of lower alkyl acrylateunits and -65 parts of methyl methacrylate units.

14. A method according to claim 12 in which the lower alkyl acrylate isethyl acrylate.

15. A method according to claim 12 wherein the thermosetting coatingpowder contains 5-20 parts of (2) and 5-40 parts of (3).

16. A thermosetting coating powder composition containing 1. 100 partsof a solid, low molecular weight, substantially linear, storableepoxy-functional acrylic terpolymer of 5-20 parts glycidyl methacrylateunits, 5-35 parts of lower alkyl acrylate units in which the alkyl groupcontains from two to four carbon atoms, 50-70 parts of methylmethacrylate units, and 0.5-10 parts of chain tenninating groupsselected from nor'icmswherein R is an isooctyl group, said terpolymerhaving a. a glass transition temperature of from 20 to b. a Durransmelting point of from to 170 C.,

c. a melt index of from 1 to 30, at a temperature of 152 C., with apiston loading of 1,200 grams and an extrusion orifice of 0.0465 inches,and

d. an epoxy equivalent weight of 700-3,000

2. 0-20 parts of a crosslinking agent selected from saturated aliphaticdicarboxylic acids having from I fiye t c 20 carbon atoms which isessentially unreactive at room temperature but which reacts rapidlyabove 150 C.

3. 0-40 parts of a butanediol adipate having an equivalent weight percarboxyl group of from to 1,500,

4. 0.1 to 5 parts of poly 2-ethy1 hexyl acrylate and 5. 1-10 parts ofglyceryl tris(12-hydroxy-stearate),

provided that the ratio of total carboxyl equivalence of (2) plus (3) is0.5-1.5:1 of the epoxy equivalenceof(1).

2. 7-8 parts of an aliphatic dicarboxylic acid containing nine to 10carbon atoms,
 2. 0-20 parts of a crosslinking agent selected fromsaturated aliphatic dicarboxylic acids having from five to 20 carbonatoms which is essentially unreactive at room temperature but whichreacts rapidly above 150* C.
 2. 7-8 parts of an aliphatic dicarboxylicacid containing 9-10 carbon atoms,
 2. 0-20 parts of a crosslinking agentselected from saturated aliphatic dicarboxylic acids having from five to20 carbon atoms which is essentially unreactive at room temperature butwhich reacts rapidly above 150* C.
 2. A method according to claim 1wherein the coating powder is an acrylic coating powder.
 2. 0-20 partsof a crosslinking agent selected from saturated aliphatic dicarboxylicacids having from five to 20 carbon atoms which is essentiallyunreactive at room temperature but which reacts rapidly above 150* C. 2.0-20 parts of a crosslinking agent selected from saturated aliphaticdicarboxylic acids having from five to 20 carbon atoms which isessentially unreactive at room temperature but which reacts rapidlyabove 150* C.
 3. 8-12 parts of butanediol adipate having an equivalentweight per carboxyl group of 500-1,000, and
 3. A method for improvingthe leveling properties of a thermosetting coating powder containing 3.0-40 parts of an acid-terminated linear polyester plasticizer-curativehaving an equivalent weight per carboxyl group of from 100 to 1,500 and3. 0-40 parts of an acid-terminated linear polyesterplasticizer-curative having an equivalent weight per carboxyl group offrom 100 to 1,500,
 3. 0-40 parts of a butanediol adipate having anequivalent weight per carboxyl group of from 100 to 1,500 and
 3. 8-12parts of butanediol adipate having an equivalent weight per carboxylgroup of 500-1,000,
 3. 0-40 parts of a butanediol adipate having anequivalent weight per carboxyl group of from 100 to 1,500,
 4. 0.1 to 5parts of a non-ionic aliphatic poly acrylate surface active agent,provided that the ratio of total carboxyl equivalence of (2) plus (3) is0.5-1.5:1 of the epoxy equivalence of (1), said method comprisingincluding in the said powder, as an additional constituent thereof 4.0.1 to 5 parts of a non-ionic aliphatic poly acrylate surface activeagent and
 4. 1-2 parts of poly 2-ethyl hexyl acrylate and
 4. A methodaccording to claim 3 wherein the terpolymer contains 10-15 parts ofglycidyl methacrylate, 20-25 parts of lower alkyl acrylate units and60-65 parts of methyl methacrylate units.
 4. 0.1 to 5 parts of poly2-ethyl hexyl acrylate, provided that the ratio of total carboxylequivalence of (2) plus (3) is 0.5-1.5:1 of the epoxy equivalence of(1), said method comprising includinG in the said powder, as anadditional constituent thereof
 4. 0.1 to 5 parts of poly 2-ethyl hexylacrylate and
 4. 1-2 parts of poly 2-ethyl hexyl acrylate, said methodcomprising including in the said powder, as an additional constituentthereof
 5. 3-4 parts of glyceryl tris(12-hydroxy-stearate).
 5. 1-10parts of glyceryl tris(12-hydroxy-stearate), provided that the ratio oftotal carboxyl equivalence of (2) plus (3) is 0.5-1.5:1 of the epoxyequivalence of (1).
 5. 1-10 parts of glyceryl tris(12-hydroxy-stearate).5. A method according to claim 3 in which the lower alkyl acrylate isethyl acrylate.
 5. 1-10 parts of glyceryl tris(12-hydroxystearate). 5.3-4 parts of glyceryl tris(12-hydroxy-stearate).
 5. 1-10 parts ofglyceryl tris(12-hydroxy-stearate). provided that the ratio of totalcarboxyl equivalence of (2) plus (3) is 0.5-1.5:1 of the epoxyequivalence of (1).
 6. A method for improving the leveling properties ofa thermosetting coating powder containing
 7. A method according to claim3 wherein the thermosetting coating powder contains 5-20 parts of (2)and 5-40 parts of (3).
 8. A thermosetting coating powder composition ofwhich the prepolymer portion is selected from epoxy, acrylic andpolyester prepolymers, said composition including from one to 10 partsby weight of glyceryl tris(12-hydroxystearate), based on 100 parts ofthe prepolymer portion of the composition.
 9. A thermosetting coatingpowder composition containing
 10. A thermosetting coating powdercomposition containing
 11. A composition according to claim 10 whichcontains 5-20 parts of (2) and 5-40 parts of (3).
 12. A method forimproving the leveling properties of a thermosetting coating powdercontaining
 13. A method according to claim 12 wherein the terpolymercontains 10-15 parts of glycidyl methacrylate, 20-25 parts of loweralkyl acrylate units and 60-65 parts of methyl methacrylate units.
 14. Amethod according to claim 12 in which the lower alkyl acrylate is ethylacrylate.
 15. A method according to claim 12 wherein the thermosettingcoating powder contains 5-20 parts of (2) and 5-40 parts of (3).
 16. Athermosetting coating powder composition containing